1. Field of the Invention
The present invention relates to a method for improving the germline transmission efficiency in aves, more particular, to a method for improving the germline transmission efficiency of avian primordial germ cells (PGCs), and methods for producing avian chimeras and transgenic using it.
2. Description of the Related Art
The migration pattern of avian primordial germ cells is very different from that of mammals and this unique mode allows producing germline chimeras by the injection of primordial germ cells into the blood vessel of recipient embryos. Primordial germ cells, which are the progenitors of functional gametes after sexual maturity, first originate from the epiblast in the blastoderm and translocate to the hypoblast of the area pellucida (1,2). During the gastrulation, they circulate through the vascular system and finally colonize into the gonadal anlagen (3). Previous reports showed that the transfer of primordial germ cells collected from germinal crescent (4,5) or blood vessel (6) into recipient embryos could produce germline chimeras. However, the number of primordial germ cells provided for transplantation was extremely limited when collected from those embryonic tissues.
It has been known that primordial germ cells lose their migration activity after settling down into the gonad. Chang et al. (7) reported, however, that primordial germ cells from the embryonic gonads, which have passed beyond the migration stage, could also induce germline transmission after being transferred into the recipient embryos at the migratory stage.
As a potent bioreactor, transgenic avian might be more applicable to biotechnology and medicine than transgenic mammals (8). Since avian germ cells migrate into the embryonic gonads through the vascular system, germ cell-mediated germline chimeras have been considered as one of the efficient tools for inducing avian transgenesis. Several attempts were made for producing chicken germline chimera to date (6, 9, 10) and a gonadal primordial germ cell (gPGC) transplantation system has been developed for overcoming a lot of difficulties in the production of transgenic poultry (7, 11, 12). Our previous study (7) first reported the germline chimera production by transfer of chicken gPGCs, which confirmed that primordial germ cells nested in the embryonic gonads could regain migration activity by transplantation into the embryos at earlier stage. However, the germline transmission efficiency remained low leveling the previous study. Therefore, there remains a need in the art for improving germline transmission efficiency in gPGC-derived chicken chimeras.
Throughout this application, various patents and publications are referenced and citations are provided in parentheses. The disclosure of these patents and publications in their entities are hereby incorporated by references into this application in order to more fully describe this invention and the state of the art to which this invention pertains.